QuickFIX is the worlds first Open Source C++ FIX (Financial Information eXchange) engine, helping financial institutions easily integrate with each other.
The SVN repository is now locked. Latest code is hosted at github.
https://github.com/quickfix/quickfix

QuickFIX/J is an 100% Java implementation of the popular QuickFIX open source FIX protocol engine. QuickFIX/J features include support for FIX protocol versions 4.0 through 4.4 and 5.0/FIXT1.1 (www.fixprotocol.org).
Please note that the SourceForge SVN repo is read-only. Current repo can be found here: https://github.com/quickfix-j

Barbecue is a Java library that enables the creation of barcodes in a variety of standard formats that can be displayed as Swing/AWT components, included in printed output, generated as EPS and SVG and displayed in a web application.

XLW is a C++ wrapper for the Excel C API described in the Microsoft Excel 97 Developer's Kit. It makes xll programming automatic. Its powerful interface will empower your C, C# or C++ numerics by embedding them in Excel just like the built-in functions.

JQuantLib provides a free, open-source and comprehensive framework for quantitative finance. It's a 100% Java translation of QuantLib, which is written in C++. JQuantLib provides pricing valuation of a wide range of asset classes, methods and models

QLNet is a financial library written in c# for the Windows enviroment derived primarily from its C++ counterpart, Quantlib, which has been used as a base reference for modelling of various financial instruments.

Lokad provides business forecasting services. Get started with sales forecasting, inventory optimization, or staff planning! http://www.lokad.com - This project has been migrated to GitHub, check https://github.com/Lokad/lokad-sdk

Read data from Excel 97+ spread sheets without Microsoft! Provides an API to write applications that read Excel documents. The xlreader tool converts data to tab delimited, CSV or SQL inserts. Written in C. Based on the the Java version by Andrew Khan.

Trad4 is a fully concurrent, thread safe, graph-based programming language that scales linearly on multiple cores. It is initially intended for deployment in the financial industry to model real-time risk.